1. Technical Field
The invention relates to a control pedal unit for a vehicle such as an accelerator, brake, clutch or other type of root control pedal. In particular, the invention relates to a control pedal unit in which it is desired to eliminate the conventional return means, such as a return spring, that biases the pedal toward its unloaded or non-depressed state. In another aspect, the invention relates to a control pedal unit for a vehicle which decreases the risk of foot injury to the driver in an accident. The invention furthermore relates to a support structure for housing at least two control pedal units having the characteristics described above, as well as a vehicle that includes such a control pedal unit. Method and apparatus for sensing the position and change in position of a control pedal unit is also included for purposes of controlling the vehicle.
2. Background Art
Conventional vehicular brake systems typically include a pivotally hinged lever constituting a pedal. The lever is attached to a push rod that actuates a piston housed in a master cylinder. The piston is biased toward an unactuated or non-depressed position by a master cylinder return spring. The master cylinder return spring therefore also returns the pedal to its non-depressed position when a driver releases pressure on the pedal.
Accelerator pedal units are known for automotive vehicles that incorporate electronic engine management systems for which a pedal position sensor determines the degree of depression of the accelerator pedal. Such accelerator pedal units furthermore include a return spring for returning the pedal to a rest position when released after being depressed by a driver. In operation, the sensor controls the vehicle""s power plant if the return spring breaks or malfunctions. An example of such a system is found in EP 322,785.
Other known mechanisms associated with vehicle control pedals include U.S. Pat. No. 4,009,623 that relates to a foot lever construction having controlled flexibility. The flexibility is provided for reducing the negative effect when over-exerting forces are applied to the lever due to excitement of the driver under racing conditions. A foot pedal linkage is disclosed in EP 830,989 that is arranged between a push rod connected to the pedal arm and which provides a break-away feature for, in the event of an accident, releasing the connection between the push rod and the pedal arm. This countermeasure prevents the push rod from pushing the pedal arm further into the passenger compartment during an accident thereby reducing the risk of foot injury to the driver. In DE 4340633, a link mechanism retracts the pedals in the case of an accident. This countermeasure reduces the risk of foot injury for the driver when the driver is forced in the forward direction of the vehicle.
Each of the above mentioned disclosures make use of traditional control pedal designs where a pedal is arranged as a rigid lever arm that is pivotally attached upon a support structure. The pedal is returned to its rest position by a return spring that acts either directly or indirectly on the lever. The use of such systems are particularly vulnerable when a position sensor is used for determining the degree of desired acceleration if the spring breaks as indicated in EP 322,785.
Furthermore, by arranging a control pedal unit as a pedal positioned on a lever protruding into the compartment of the vehicle, the risk of foot injury is increased for several reasons. If a traditional linkage that includes push rods is used, the pedals can, in the case of an accident, be forced into the passenger compartment with considerable force resulting in foot injury to the driver. If a device according to EP 830,989 is used, this risk may be reduced or eliminated, but foot injuries can still occur if a foot of the driver twists against the pedal when he or she is forced in the forward direction of the vehicle. A possible result of the driver being forced in the forward direction while the foot remains on such a pedal is that the foot is twisted either backwards or sideways, or in both directions. The reason for such twisting is that the pedal does not give adequate support for the foot and because the pedal is protruding into the passenger compartment. Thus, it is possible that a part of the foot will remain on the pedal in the case of an accident, while another part is forced forward without any support.
In view of the above described deficiencies associated with known foot pedal support designs, the present invention has been developed to alleviate these drawbacks and provide further benefits to the user. These enhancements and benefits are described in greater detail hereinbelow with respect to several alternative embodiments of the present invention.
The present invention in its several disclosed embodiments alleviates the drawbacks described above with respect to conventionally designed foot pedal support arrangements and incorporates several additionally beneficial features. Such features include providing a control pedal unit in which the pedal itself is formed as a resilient body thereby establishing a pedal unit in which the need for a separate return spring is eliminated. Safety is also increased because the dimensions and stability of the pedal of the present invention eliminates the risk of return spring failure. If an accident should occur in which the driver is forced towards the pedal arrangement, the resiliency of the pedal functions as a deceleration mechanism that decelerates the foot and lower leg portion of the driver in a controlled manner.
In another aspect, by providing a control pedal which includes a support structure having a lower support member and an upper support member, it is possible to establish a foot pedal that gives a driver""s foot full support from the heel to the toes. Furthermore, the design of the present invention makes it possible to construct a pedal arrangement in which undesirable projection into the passenger compartment by the arrangement is essentially eliminated. Instead, the pedal arrangement defines a continuous curved surface. This construction reduces the risk of twisting the driver""s foot in the event of an accident.
By providing a control pedal unit where the resilient body is pivotally attached to a support structure at one or both of its top and/or bottom ends, it is possible to create a pedal with sufficient operating resiliency, while also reducing the total length of the pedal. This is advantageous due to the lack of space in the feet receiving area or compartment of a vehicle.
By providing a control pedal unit where the resilient body is rigidly attached to the support structure, it is possible to create a resilient pedal supported only at one end. Such a pedal might give an appearance that reminds one of a traditional pedal design, but maintains the benefit of being itself of resilient construction which, in the case of an accident, will reduce the risk for foot injury in the ways described herein.
By providing a curved resilient body that is convexly arranged toward the driver when mounted in the vehicle, it is possible to create a pedal unit that has adequate flexure under those loads experienced during both normal and accident conditions.
By providing a flexible and symmetrical pedal body in which a bulge of the resilient convex body performs a linear displacement perpendicular to a plane including the points where the flexible body is attached to the support structure, further beneficial performance is achieved.
By making the resilient body with one bulge, an advantage of symmetry is obtained while maintaining a simple and appealing structure.
By making the flexible link so that flexure of the link increases with increasing load thereupon, a stable structure is created in which the driver is not surprised by erratic behavior of the pedal.
The use of a resilient body as a vehicular control pedal structure is particularly suited when a strain gage is employed as means for measuring or indicating the pedal""s position or condition. If a conventional pedal construction is used, the pedal position cannot be directly indicated by a strain gage. Instead, the conventional pedal must be arranged to bend a separate body whose degree of flexure may in turn be measured by a strain gage. The use of the resilient body of the present invention, together with a strain gage, renders possible a simple, reliable pedal arrangement that further includes the benefits of resiliency in a crash situation.
In another embodiment, a support structure is utilized that houses pedal units. By arranging two or more pedals so that a continuous pressing surface is created thereby, the risk for sideways twist of the foot of the driver is reduced in the case of an accident. By additionally providing means for preventing access to underneath the continuous engagement surface when an adjacent pedal is depressed, the safety aspects of the pedal assembly in an accident situation are further improved. The need for such a prophylactic against foot access underneath a foot pedal has been learned from situations in which a driver""s foot has been injured when projected underneath a conventionally designed pedal assembly in an accident.
By making the unactuated position of the pedal structure adjustable, it can easily be adapted to drivers of different height, thereby reducing the need for a shorter driver to be positioned in an excessively low position which can be detrimental to sight conditions for that driver.
The beneficial effects described above apply generally to the exemplary devices and mechanisms disclosed herein for a resiliently constructed vehicle control pedal. The specific structures through which these benefits are delivered, however, will be described in detail hereinbelow.